Inertia type switch with coaxial conductive springs

ABSTRACT

A motion sensor for sensing shocks, vibrations or the like utilizing a pair of contacts mounted on vibratory supports so that when the supports vibrate the contacts close, completing an electrical circuit. The vibratory supports and the contacts are such that the quiescent deflections of the two supports in response to constant forces move the two contacts by the same amount to maintain a constant quiescent spacing between the contacts and hence a constant sensitivity of the device to shocks, vibrations or other irregular motions. The sensitivity is therefore constant for a wide range of different quiescent orientations of the device.

Unit tates Lottus INERTIA TYPE SWITCH WITH COAXIAL CONDUCTIVE SPRINGS[75] Inventor: Peter J. Loftus, Middletown, Pa.

[73] Assignee: Alcotronics Corporation, Mt. Laurel Township, NJ.

[22] Filed: Nov. 12., 1971 [21] Appl. No.: 198,219

ZOO/61.50, 61.51, 61.52, 61.53, 61.74, 61.78, 166 BA, 166 J, 61.45 R

[5 6] References Cited UNITED STATES PATENTS [451 May 1, 1973 2,132,11110/1938 Honegger ..200/61.49 3,581,028 5/1971 Valbona.... ..200/l66 J X3,001,039 9/1961 Johnson ..200/6l.5l X 3,193,628 7/1965 Wanlass..200/l66 BA X FOREIGN PATENTS OR APPLICATIONS [5 7 ABSTRACT A motionsensor for sensing shocks, vibrations or the like utilizing a pair ofcontacts mounted on vibratory supports so that when the supports vibratethe contacts close, completing an electrical circuit. The vibratorysupports and the contacts are such that the quiescent deflections of thetwo supports in response to constant forces move the two contacts by thesame amount to maintain a constant quiescent spacing 3 527 906 9 1970Schwab ..200/61.45 R UX between the Contacts and hence a ConstantSensitivity 3,649,787 3/1972 Kasabian ..200/61.45 R of the device toShocks, vibrations of other irregular 3,141,936 7 19 4 Boyle r 1 200 1 5motions. The sensitivity is therefore constant for a 2,076,251 4/1937Rockola ....200/61.5l wide range of different quiescent orientations ofthe 2,662,945 12/1953 Cockram ..200/6l.48 device, 2,666,822 l/1954Pelletier et al. 1 ..200/166 BA X 2,947,830 8/ 1960 Goss ..200/61.51 5Claims, 18 Drawing Figures I A 1\1\\\1\o\-\ -0- Patented May 1, 19733,731,022

4 Sheets-Sheet 1 WEE? uuuuuu i I Patented May 1, 1973 3,731,022 I I 4Sheets-Sheet 2 Patented 'May 1, 1973 v 3,731,022

4 Sheets-Sheet 5 Patented May 1, 1973 4 Sheets-Sheet 4 FIGI.

ggy, V/Z'ZH Uzi 4 INERTTA TYPE SWITCH WITH COAXTAL CONDUCTIVE SPRTNGSBACKGROUND OF INVENTION forces acting thereon. In a preferred form, theinvention relates to improved electrical contacting means for operatinga pair of contacts in response to changes in acceleration of the base onwhich the contacts are supported.

There are a variety of applications in which it is desired to detect andprovide indications of changes in the acceleration or in thegravitational field acting on a body. One specific use of such devicesis in the sensing of the disturbance of the position of an object, or indetecting mechanical vibrations transmitted into the object.

One example of a practical application of such a device is in thedetection of unauthorized movement of a portable object such as avehicle. For example, a motion sensor installed upon a bicycle or othervehicle left unattended may be used to provide indications ofunauthorized disturbance of the position of the vehicle so as to soundan alarm. Another practical use for such a motion sensor comprisesdetecting the presence of a trespasser by mounting a motion sensor sothat sudden deflections or vibrations due to the presence of thetrespasser are transmitted to the motion sensor. Military applicationsinclude, for example, motion-sensing fuses for land mines or for boobytraps, and explosion sensors.

There are a variety of devices known for performing one or more of theabove-identified functions. For example, it is known to employ a pair ofcontact structures, one of which is spring-mounted so that itscontacting relation with the other contact changes in response tocertain changes in the inertial and gravitational forces appliedthereto. One form of such device may comprise a resilient spring forsupporting a contact normally spaced from another fixed contact in suchmanner that a change of acceleration of the base on which the spring issupported will cause the spring deflection to change and close thecontacts. A voltage applied between the two contacts will then cause acurrent to flow, which may be used as an indication of the motioncausing the contacts to close. More particularly, such a spring may havedifferent predetermined deflections for different steady accelerationsor for different steady values of gravitational forces acting thereon,and the fixed contact will then serve to detect the extent of thissteady deflection and thereby provide an indication of the gravitationaland inertial force existing at that time. If such a spring device isresilient but not vibratory, i.e., is so heavily damped or so lossymoves between two different deflection positions produced by twodifferent values of forces acting thereon without performing substantialoscillation, then the force for which the contacts are closed dependsentirely upon the quiescent deflection characteristics of the spring.

A-greater sensitivity, and a greater responsiveness to changes in motionof brief duration, are obtained when a vibratory spring arrangement isutilized for one of the contacts. With such an arrangement, a suddenchange in the forces acting on the spring element will excite it intovibrations on either side of its quiescent deflection position, and ifthe force applied thereto thereafter remains constant at the new value,the oscillations will die out in a time depending upon the effectivemechanical Q of the resonant spring element. Since the excursions inposition of the spring member during such oscillations extend beyond thequiescent deflection positions thereof, the fixed contact may be placedso as to be contacted by the vibrating contact when it swings beyond itsquiescent deflection position; or, viewing the matter from anotheraspect, for a given spacing between the two contacts, relatively smallerchanges in applied forces will accomplish at least an instantaneous orintermittent contacting between the two contact elements than if onewere to rely entirely upon the quiescent or static deflection of thespring element.

With such a vibratory structure then, the response of the structure to achange from a first to a second level of forces acting thereon in adirection along which it is capable of deflection, comprises an initialtransient oscillatory or vibratory phase beginning at the time of thechange in applied force, plus a steady-state or quiescent deflection ofthe resilient spring, the oscillations or vibrations thereafter dyingdown while the quiescent deflection continues so long as the new valueof applied force continues at a steady value. Usually a spring devicewill be both resilient in the sense that it tends to return to itsoriginal rest position when a deflecting force is applied and thenremoved, and also vibratory in that it will react to the change inapplied force to execute transient oscillations or vibrations. However,a resilient spring device need not be vibratory, since if it issufficiently severely damped it will return to its original positionwhen a deflecting force is removed, but will not vibrate substantiallypast that rest position.

While a fixed contact and an adjacent resilient, vibratory contactstructure may be used as a motion sensor, in certain types ofapplications such an arrangement will have substantial drawbacks orlimitations. 1 have found that such limitations or drawbacks ariseparticularly in applications in which the change in contact spacingproduced by the quiescent or steady-state deflection of the spring isunnecessary and undesirable for the particular purpose; suchapplications occur where one is not interested in measuring the valuesof steady forces acting on the spring member, but merely wishes to sensechanges in such forces, and the steady force component thus merely tendsto obscure, or render less reliable, reproducible or accurate, thedesired sensing of force changes.-

As an example, consider a contact mounted on a spring and adjacent asecond fixed contact, so that upon sufficient deflection of the springthe contacts will be closed. Also assume that the spring is mass loadednear one end, so as to increase the amplitude of its oscillations. Sucha device, when placed in a gravity field, typically will have a staticor quiescent deflection due to the action of the gravity field on themass secured to the spring, and the extent of its deflection will varydepending upon the orientation of the structure with respect to thedirection of gravity because the magnitude of the component of gravitydirected transverse to the spring will vary. As a result, the spacingbetween the two contacts will also vary depending upon the orientationof the assembly with respect to the direction of gravity, and theamplitude of oscillation required to close the contacts will thereforealso vary depending upon the orientation. Accordingly, the sensitivityof the device to changes in forces such as shocks or vibrations, forexample, will vary with its orientation. There are a variety ofapplications in which it is desired that the sensitivity of such anassembly remain substantially constant, and yet that it be capable ofuse under different conditions of orientation with respect to thedirection of gravity.

In one particuiar application with specific reference to which theinvention will be described, a motion sensor is secured to a vehiclesuch as a bicycle so that when the bicycle is left unattended the sensorcontacts remain open until such time as an unauthorized person may movethe bicycle, thereby setting a springmounted contact into oscillation sothat, near one extreme of its vibration, it touches the other contact toclose an electrical circuit and sound an alarm. However, because thebicycle may be left in a large variety of orientations, the sensor willalso have different orientations at such times, the component of gravitytending to close the switch contacts will be different, and accordinglythe quiescent spacing between the contacts when the bicycle is leftunattended will depend upon the rest orientation of the bicycle. Thismeans that the sensitivity to changes in force, due to later non-uniformmotion of the bicycle during its unauthorized removal, will also bedifferent for different orientations. If the spacing of the contacts hasbeen set in manufacture at such a large value as to prevent closing uponany fixed orientation thereof, then the device will be relativelyinsensitive, while if it is originally set so as to exhibit the desiredhigh degree of sensitivity in one orientation thereof, the contacts mayclose when it is placed in a different fixed orientation, giving a falsealarm.

Accordingly, in such an application the quiescent deflection of thespring not only changes the contact spacing unnecessarily, but in factintroduces an undesirable variation in the sensitivity of the device. Itis then desirable to eliminate the effect of steady forces on thespacing between the contacts, while retaining sensitivity to changes insuch forces due for example to shocks, vibrations, or other rapidchanges in accelerations.

Accordingly, it is an object of the invention to provide a new anduseful motion sensor.

Another object is to provide such a motion sensor which responds tochanges in the inertial and gravitational forces acting thereon, atleast along certain sensitive directions thereof, and yet is relativelyinsensitive, within predetermined ranges, to different steady values ofsuch forces.

A further object is to provide such a sensor which is simple,inexpensive, compact and reliable.

A further object is to provide such a sensor which is purely mechanicalin nature and requires no sliding parts or complicated mechanisms.

Another object is to provide a new and useful motion sensor whichresponds with substantially constant sensitivity to changes in theinertial and gravitational forces acting thereon, at least along one ormore directions therein, when placed in different fixed orientations. a

A further object is to provide a motion sensor of the vibratory contacttype which has a substantially constant sensitivity over a wide range oforientations with respect to a gravity field in which it is located.

SUMMARY OF THE INVENTION These and other objects and features of theinvention are accomplished by the provision of a motion sensor of theclass comprising first contact means, first support means for said firstcontact means, second contact means positioned adjacent the said firstcontact means, and resilient vibratory means supporting said secondcontact means so as to change its state'of contact with respect to saidfirst contact means when said vibratory means vibrate, which sensorcomprises the improvement whereby said first support means is alsoresilient so as to be deflected in the same sense as said vibratorysupport means in response to steady inertial and gravitational forcesacting thereon. Preferably the quiescent deflection characteristics ofthe first support means and of the vibratory support means are such thatthe contact means are deflected by substantially the same amount and inthe same sense in response to different steady values of the componentof gravitational and inertial force applied along a sensitive directionof the sensor, so that the spacing between the first and second contactmeans remains substantially fixed in the quiescent state of the sensor.The amplitude of vibration of one or both of the support means requiredto cause contactingbetween them is then substantially independent ofsuch steady forces applied thereto. Where the above-mentioned differentvalues of the component of steady gravitational and inertial forces aredueto different orientations of the motion sensor with respect to thedirection of gravity, the quiescent contact spacing and the sensitivityof the device to changes in accelerations due to shock, vibration, orsimilar irregular movement, then remainsubstantially the same despitedifferences in the orientation of the sensor at different times.

Preferably the resilient first support means is also vibratory, andpreferably it has a vibration period differing from that of theaforesaid vibratory means so that the possibility of their vibrating inphase, and out of contact with each other, for any appreciable period oftime is eliminated.

The preferred form of the sensor means of the invention will thereforehave a sensitivity to changes in acceleration which is substantially thesame regardless of the orientation of the sensor over at least a rangeof orientations thereof. Accordingly it will preserve the samesensitivity when the object on which it is mounted is placed indifferent orientations, or when it is mounted in any of a variety oforientations on a fixed object. In applications of the latter type,substantial practical advantages result from the fact that the sensormay be installed without requiring special critical mounting proceduresand without the need to provide special orientations of mountingsurfaces.

BRIEF DESCRIPTION OF FIGURES These and other objects and features of theinvention will be more readily understood from a consideration of thefollowing detailed description, taken in connection with accompanyingdrawings, in which:

FIG. 1 is an elevational view illustrating one use of the motion sensorof the invention in a bicycle alarm;

FIG. 2 is a block diagram showing the electrical function of the motionsensor in an alarm system;

FIG. 3 is a vertical section through one form of motion sensor embodyingthe invention;

FIG. 4 is a view taken along lines 44 of FIG. 3;

FIG. 5 is a fragmentary sectional view of a portion of the sensor ofFIG. 3 as it appears when making electrical contact during use;

FIGS. 6 and 7 are perspective views of the spring loading masses in thesensor of FIG. 3;

FIG. 8 is a vertical section of another form of sensor according to theinvention;

FIG. 9 is a side view, partly in section, of another form of theinvention using leaf springs;

FIG. 10 is a view taken along line ltl-l0 in FIG. 9;

FIGS. 11 thru 14 are schematic side views showing the contactingarrangements usable in the device of the invention; I

FIG. 15 is a schematic side view of another form of the invention.

FIGS. 16 and 17 are vertical sections of another form of the invention,shown in two corresponding different orientations; and

FIG. 18 is a vertical sectional view of another form of the invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS Referring now to theparticular embodiments of the invention illustrated in the drawings byway of example only, FIG. 1 illustrates a bicycle 10 having an alarmsystem 12 mounted on the frame element 14 by means of a clampingarrangement 16. As represented in FIG. 2, the alarm system may comprisea suitable battery 18 supplying operating current to alarm apparatus 20when the sensor switch 22 is closed, but not when it is open. The sensorswitch 22 is part of the motion sensor 24 mounted within the outercasing of the alarm system 12 in FIG. 1. Suitable circuitry for theelectrical system of FIG. 2 is shown and claimed, by way of example, inthe copending application, Ser. No. 144,104 of IF. Bash and R.W. I-Iorn,filed May 17, 1971 and of common assignee herewith. In general, thebicycle is normally left in a fixed rest position by its owner with thesensor switch contacts open so that no alarm occurs, but if the sensorswitch contacts are closed, even momentarily, the alarm will be soundedand will continue thereafter for a predetermined length of time. Sincesuitable electrical circuitry for operating an alarm in response toclosing of the switch contacts are known, and described for example inthe above-cited copending application, the details of such circuitryneed not be set forth herein.

Referring now to the particular form of the motion sensor 24 which isillustrated in FIGS. 3-5, an electrically insulating base means 30supports an outer cylindrical shell of electrically insulating material32. Also mounted on the base means 30 inside of the outer casing 32 aretwo coil springs 34 and 36.

Coil spring 36 is mounted so that, in the absence of lateral deflectingforces, its longitudinal axis extends along the axis AA of the outercasing 32. At its righthand end spring 36 surrounds closely acylindrical surface portion 38 of the base means 30, and is held fixedthereto by the slideable insulating ring 40 surrounding the outercylindrical surface of the right-hand end of the spring. Ring 40 may beadjusted axially to adjust the length of spring 36 cantilevered to theleft of ring 40, this being the portion of the spring which is then freeto deflect laterally. The last turn 42 of spring 36 extends outwardlythrough an opening 44 in the outer casing 32 to an external contact 46connecting with electrical lead 48.

The left hand end of spring 36 is provided with a loading mass 49 in theform of a centrally apertured ring of metal. The leftmost coil of thespring 36 fits tightly into the annular peripheral recess 49a in mass 49to hold the latter mass to the spring.

The spring 34 is mounted on base means 30 by means of the bore 50extending axially through base means 30, the spring 34 forming a closespring fit with the interior of bore 50 yet permitting slidingadjustment of the axial position of the spring so as to set the lengthof the spring which is cantilevered to the left of the inner end 52 ofthe base means 30. The right-most end of spring 34 has a reduceddiameter portion terminating in a pigtail extension 54, to whichelectrical lead 55 is soldered or otherwise secured in a manner toprovide electrical contact therewith.

Spring 34 extends axially through the center of the aperture in thecenter of mass 49, and is provided at its leftmost end with the loadingmass 56, secured thereto by means of the annular depression 58 intowhich the last coil of spring 34 extends.

The motion sensor of FIG. 3 is such that if it is so oriented that themass 56 hangs directed downwardly in a gravity field, the axis of bothof springs 36 and 34 will extend along the axis AA of the outer casing32. The inner surface 60 of the mass 49 comprises one electrical contactof the sensor, and the adjacent outer surface of spring 34 constitutesthe other contact, and when these two surfaces contact each other anelectrical circuit is completed between the leads 48 and 55.

If the motion sensor FIG. 3 is thus oriented with weight 56 directeddirectly downwardly in a gravity field, the spacing between contactsurface 60 of mass 49 and the adjacent outer surface of spring 34 willbe substantially the same as is shown in FIG. 3 wherein the axis of themotion sensor is at right angles to gravity, i.e., horizontal. Moreparticularly, in the orientation shown in FIG. 3, both of the springs 34and 36 are deflected downwardly by the action of gravity on therespective masses 56 and 49. However, the weights of the masses and thefree lengths and stiffnesses of the springs 34 and 36 are selected sothat, in the quiescent steady state conditions in a gravity field,spring 34 still passes substantially through the center of the openingin mass 49 and the inter-contact spacing remains the same. Similarly forother angular orientations of the sensor of FIG. 3, this spacing issubstantially constant after the sensor has been left steady for a shortlength of'time.

However, if the base means 30 is subjected to a change in accelerationso as to change the inertial forces acting on the masses S6 and 49, orif the gravitational field should change substantially, both of thesprings 34 and 36 will be set into oscillation transversely of theirlengths and electrical contact will quickly occur as shown in FIG. 5,wherein the mass 49 has vibrated sufficiently upwardly relative tospring 34 that its contacting surface 60 is in electrical contact withthe lower side of the exterior of spring 34, thereby to close theelectrical circuit between leads 48 and 55 at such time.

Because the quiescent spacing between the contact surface 60 and theouter contact surface of the spring 34 is the same for a wide range ofvariation of the angle of the sensor, with respect to an axisperpendicular to the plane of the figures, the sensitivity of the sensorto vibration or shock also remains substantially constant in thesedifferent orientations.

It is also noted that in the embodiment of FIGS. 3-5 the annular contactsurface 60 surrounds the circular outer surface of spring 34 to providea symmetrical arrangement about the longitudinal axis of the sensor,such that the sensitivity thereof also remains substantially constantfor different orientations thereof about its longitudinal axis.

In the preferred arrangement, the natural periods of vibration of themass-loaded springs 36 and 34 differ from each other, so as to avoid thepossible condition in which both springs might oscillate at the samefrequency and in the same phase at least for substantial periods oftimes, so as to delay or possibly even prevent their coming intoelectrical contact, although in many applications such a condition isunlikely to arise because of differences in starting phases of theoscillations of the two springs.

Thus when the motion sensor of FIG. 3 is installed as shown at 24, FIG.1, the bicycle may be left vertical or nearly vertical, or left lying onits side or at some intermediate angle, with the alarm system turned on.Normally the alarm would not be turned on until the transient vibrationsof the springs have substantially disappeared; if the alarm is turned ontoo soon, and spring vibrations cause closing of the contacts andsounding of the alarm, the system may then be turned off for a shortperiod by the operator to allow the vibrations to subside further. Ifone thereafter attempts to steal the bicycle, even very slightirregularities in motion of the bicycle during such unauthorized removalwill set the springs into vibration, causing the contacts to close andthe alarm to be sounded. The contacts may be set very close together forhigh sensitivity, since different angles at which the bicycle is leftwill produce different quiescent deflections of one of the springs but acorresponding quiescent deflection of the other spring, so as tomaintain the contact spacing and sensor sensitivity the same for thesedifferent orientations, as desired.

Without thereby in any way limiting the scope of the invention, thefollowing example of an embodiment of the form of the invention shown inFIG. 3 is provided in the interest of complete definiteness. Spring 36may have a coil diameter of about three-eighths inch, and be composed ofphosphor bronze wire of about 0.016 inch diameter and 40 turns per inchin its unstressed state.

Mass 49 may have a weight of about 0.0025 pounds, and the free length ofspring 36 between the right-hand side of mass 49 and the left-hand sideof cylinder 40 may be about five-sixteenths inch. Spring 34 may have acoil diameter of about 0.110 inch, and be made of phosphor bronze wireabout 0.012 inch indiameter with about 56 turns per inch in itsunstressed state. The free length of spring 34 from the left-hand end 52of base means 30 to the right-hand end of the mass 56 may be aboutfive-eighths inch, and mass 56 may have a weight of about 0.001 pounds.The quiescent spacing between the contacting surface 60 and the outercontact surface of the spring 34 is typically about 0.010 inch.

FIG. 8 illustrates a variation of the motion sensor shown in FIG. 3,which may be like that shown in FIG. 3 except for the details of thearrangement of the loading masses and contacting surfaces, correspondingparts being represented by corresponding numerals with the suffix A.Here the mass 56A has been extended along and outside the center spring34A to provide a continuous solid contact surface opposite thecontacting surface 60A of mass 49A, the latter contacting surface 60Abeing extended forwardly of the latter weight. This not only provides abetter contacting surface arrangement, but also illustrates anothercontrollably variable parameter available to the designer, namely theposition of the contacting surfaces with respect to the correspondingspring elements. Thus because the contacting surface 60A is positionedto the left of the end of the spring 36A, it will experience a greaterstatic or quiescent deflection in response to steady forces, therebyenabling use of a shorter spring or lighter mass for the samedeflection, and different resonant periods for the two springassemblies. Among the principal factors in any design are thestiffnesses of the springs employed, their lengths, the masses used toload'them, and the positions and mountings of the contacts with respectto their respective spring structures.

FIGS. 9-14 illustrate embodiments of the invention utilizing leafsprings as the resilient vibratory support means for the contacts. Inthe embodiment shown in FIGS. 9 and 10, a pair of leaf springs and 72 inthe form of rectangular strips of spring material are supported on acommon support block 76. For convenience, block 76 may comprise a centerportion 76A to opposite sides of which the leaf springs 7 0 and 72 arecemented, the outer surfaces of the leaf springs then being covered bycemented end blocks 78 and 80 to hold them firmly in place and defineclearly the beginning of the free portion of each leaf spring. Leafspring 70 is loaded by a mass 82 made up of three metal blocks cementedto each other and to the leaf spring,

while leaf spring 72 is loaded by a mass 84 made up of two blockscemented onto opposite sides of it. For convenience in positioning theleaf springs with respect to the supporting block 76 and the masses 82and 84, the leaf springs, the masses and the block may be provided withappropriate positioning holes 88 whereby a pin inserted through thealigned holes during assembly will assure proper location of the variouselements.

The right-hand ends of the two leaf springs extend beyond the block 76at 90 and 92 to provide contact areas for connection to a source ofelectrical current.

Leaf spring 70 extends beyond the mass 82, as shown at 94, to provideone switch contact surface for the motion sensor, and leaf spring 72extends beyond mass 84 and is then bent into a reverted shape so as toprovide the other contact surfact 96 at a position slightly toward block76 from mass 84.

It will be appreciated that the two leaf springs 70 and 72 are deflectedin the same sense and by substantially the same amount in response tosteady forces acting thereon, such as the force of gravity, andtherefore the spacing between the contact surfaces 94 and 96 remains thesame for different steady orientations of the sensor. However, when thesupport block 76 is subjected to a change in its acceleration, as by theapplication of shock or vibration thereto, both leaf springs will beexcited into vibration generally along a direction perpendicular totheir length and width, with different vibrational periods, and contactbetween the surfaces 94 and 96 will promptly occur even for relativelysmall magnitutes of shocks and vibrations. In this embodiment thesprings 70 and 72 exhibit little or no deflection in the direction oftheir widths either in response to steady forces or in response toshocks, because of their stiffnesses in that direction. However, wherethe device is used as a sensor of unauthorized removal of property or ofthe presence of trespassers, the irregular motion transmitted to thebase 76 will in almost every case produce a component in the directionfor setting the leaf springs into oscillation, thereby closing the contacts to enable an alarm. The principal design variables I in thisembodiment are the locations and magnitudes of the loading masses, thelengths of the cantilever arms by which theweights are supported fromthe support block, and the lengths and orientations of the contactsextending from the leaf springs.

FIGS. 11-14 show schematically several variations which may be made inthe leaf-spring sensor of FIGS. 9 and 10, corresponding parts beingdesignated by the same numerals with a corresponding suffix letter. FIG.11 utilizes a-conductive contact 100 in the form of a metal stripsecured to the leaf spring 70B and positioned in line with the center ofthe mass 82B so as to contact the leaf spring 728 on the side of mass843 toward support block 768.

In FIG. 12, the contact 102 is positioned beyond and below the mass 82Cand in alignment with the center of the mass 84C, which serves as theother contact.

In FIG. 13, the leaf spring 70D is weighted at its end and leaf springs72D and 73 are symmetrically placed above and below it, the latter twoleaf springs, the

In each of the variants shown in FIGS. 11-14, the parameters of thesprings, masses and contact arms are selected so that when the sensor isoriented differently than shown in the figure, so as to change thecomponent of gravity tending to urge the contacts together, thequiescent or steady-state spacing between the contacts will remainsubstantially the same because the leaf springs are deflected similarlyby the same gravity forces under steady-state conditions. Also in eachcase a vibration, shock or similar change in acceleration imparted tothe supporting block 76 will cause the leaf springs to vibrate so as toclose the contacts, provide an electrical circuit through them, and thusproduce an electrical indication of the motion to be sensed.

FIG. 15 shows another dual leaf-spring embodiment in which the twospring-loading masses and their geometrical arrangements are identicalwith each other. While suitable for many purposes, this form of theinvention introduces the possibility that the two leaf springs willvibrate in the same phase and with the same frequency for appreciablelengths of time without conmasses 82D and 83 and their correspondingcontact arrangements being substantially identical with each other. Inthis embodiment, one external electrical contact is made to spring 70Dandthe other connection is made to both of the leaf springs 72D and 73,so that a circuit is completed when either of the opposed contacts 106or 108 touches center leaf spring 70D.

In FIG. 14, the arrangement isgenerally the same as that in FIG. 13,except that the two separate loading masses of FIG. 13 are replaced by acommon mass 110 extending between the upper and lower leaf springs 72Band 73B, mass 110 being centrally apertured to permit passagetherethrough of the center leafspring 70E. Two opposed screw contacts112 and 114 are mounted in the common mass 110 with their contacttips'pointe'd toward directly opposite sides of the leaf spring 7013.

tacting each other and, if the vibrations die down sufficiently rapidly,in some circumstances it is possible that they might not contact eachother at all in response to relatively weak shocks or vibrations.

FIGS. 16 and 17 show an embodiment of theinvention in which extension ofa coil spring is utilized to provide the vibratory motion, rather thanlateral deflection thereof. Thus the two coil springs and 122 aresupported from a common base 124, and electrical connections 126 and128, respectively, are provided at the fixed ends of the springs.Respective loading masses 132 and 134 are provided at the opposite endsof the springs, and respective contacts 136 and 138 are secured toweight 132 and to spring 122, both of which are-here assumed to beelectrically conductive also. The springs are such that, when unloaded,they have available a range of motion for both compressional andexpansional motion. Springs 120 and 122 are also provided withrespective guides 137 and 139. When the motion sensor is mounted asshown in FIG. 16, with the masses extending downwardly along thedirection of gravity, both springs will be expanded and a certainspacing will exist between the contacts. Any shock or vibration impartedto the support 124 will cause the masses to oscillate up and down, thusbrining the contacts into engagement with each other and completing theelectrical circuit.

Now if the arrangement is' turned horizontal, i.e., to the positionshown in FIG. 17 for example, the masses 132 and 134 are completelysupported by the guides 137 and 139, the interiors of which arepreferably lubricated and provide a sliding fit with the weights.Accordingly, both springs contract to their neutral state in the steadystate condition, the contacts 136 and 138 moving by the same amount soas to maintain the spacing between them the same as in FIG. 16. Again,when vibration is imparted to the support 124, the springs will causethe masses to oscillate in a horizontal direction, in turn causing thecontacts to close at least momentarily, thereby completing theelectrical circuit. The device may be placed in any of a large range oforientations without changing the spacing of the contacts understeady-state conditions, so that the sensitivity to shocks andvibrations remains substantially the same despite differences inorientation.

FIG. 18 shows an arrangement generally similar to that of FIGS. 16 and17 with the exception that identical springs and masses have beenutilized in a symmetrical arrangement, with the advantage thatuniformity of contact spacing can be assured without any special designprocedures, since the two identical structures will always operate inthe same manner in response to steady forces. However, this form has thesame possible disadvantage in some applications as does the arrangementof FIG. 15, since the two periods of vibration are the same.

As will be seen from the embodiment of FIG. 18, if

the two spring-mounted contact structures are the same, the quiescentcontact spacing is always the same, as are the resonant periods of thetwo structures. In general, if one then modifies one of the structuresto produce a difference in resonant period for the two structures, thecenters of mass of the two loading masses will move by different amountsfor different steady .forces applied thereto, and if the two contactsare mounted to move with the centers of mass of the loading masses thequiescent spacing between the contacts will also change. However, bymounting the contacts so that they move by different amounts than thecenters of mass of their corresponding loading masses, as shown in theother figures, this tendency for the quiescent contact spacing to changecan be overcome even though the resonantperiods are different.

In other embodiments of the invention load masses are not required, theweight of the spring itself causing the desired quiescent deflection andthe desired vibratory characteristics.

In the embodiments of the invention described herein in detail, the twocontacts are normally open and are closed to produce output indications.However, the invention may be embodied in devices in which the contactsare normally spring-biased in the closed condition (preferably lightly)and are opened by vibratory spring motion to produce electricalindications by breaking of an electrical circuit through the contacts.

those shown and described, without departing from the v spirit and scopeof the invention as defined by the appended claims.

What is claimed is:

1. A motion sensor, comprising:

a supporting base;

a first spring system secured to said base so as to turn with said base,said first spring system comprising first spring means supported at oneend on said base, a first spring-loading mass supported on said firstspring means at a position spaced along said first spring means fromsaid base so as to deflect said first spring means, and first electricalcontact means on said first spring means at a first point spaced alongsaid spring means from said base;

a second spring system secured to said base so as to turn with saidbase, said second spring system comprising second spring means supportedat one end on said base, a second spring-loading mass supported on saidsecond spring means at a position spaced along said second spring meansfrom said base so as to deflect said second spring means,

and second electrical contact means on said second spring system at asecond point spaced along said spring means from said base;

said first spring-loading mass being spaced further along said firstspring system than is said second spring-loading means to producedifferent periods of free vibration for said first and second springsystems and different static displacements of those ends of said firstand second spring means adjacent said 'first and second spring-loadingmeans, respectively;

said first and second electrical contacts being positioned so as to bespaced apart when said first and second spring systems arequiescent, andaligned so that the contact surfaces thereof are closed to each otherwhen said first and second spring systems are deflected sufficiently inopposite directions;

said first and second spring systems differing from each other withrespect to the values of at least one of the parameters of loading massand spring stiffness, so that the static deflections of said contactsurfaces are substantially the same for different values ofgravitational and inertial forces acting on said spring-loading masses.

2. The motion sensor of claim 1, in which said first and second springsystems are secured to said base at adjacent positions and extendtherefrom in the same direction in substantially parallel relationshipto each other.

3. The motion sensor of claim 2, in which each of said first and secondspring means comprises a cantilever-mounted leaf spring.

4. The motion sensor of claim 1, in which said first and second springmeans comprise first and second coaxial helical coil springs.

5. A motion sensor, comprising:

first coil spring means;

means mounting said first coil spring means to permit steady lateraldeflection and lateral vibratory motion thereof;

second coil spring means;

means mounting said second coil spring means to permit lateral steadydeflection and lateral vibratory motion thereof;

said first and second coil spring means having respective first andsecond contact surfaces thereon positioned so that said contact surfacesare spaced from each other by substantially a fixed distance when saidsensor is oriented in different quiescent positions but contact eachother when said first and second coil spring means are set intovibration;

said first and second coil spring means being helical and coaxial, andsaid first coil spring means being positioned inside said second coilspring means.

III I. t III

1. A motion sensor, comprising: a supporting base; a first spring systemsecured to said base so as to turn with said base, said first springsystem comprising first spring means supported at one end on said base,a first spring-loading mass supported on said first spring means at aposition spaced along said first spring means from said base so as todeflect said first spring means, and first electrical contact means onsaid first spring means at a first point spaced along said spring meansfrom said base; a second spring system secured to said base so as toturn with said base, said second spring system comprising second springmeans supported at one end on said base, a second springloading masssupported on said second spring means at a position spaced along saidsecond spring means from said base so as to deflect said second springmeans, and second electrical contact means on said second spring systemat a second point spaced along said spring means from said base; saidfirst spring-loading mass being spaced further along said first springsystem than is said second spring-loading means to produce differentperiods of free vibration for said first and second spring systems anddifferent static displacements of those ends of said first and secondspring means adjacent said first and second spring-loading means,respectively; said first and second electrical contacts being positionedso as to be spaced apart when said first and second spring systems arequiescent, and aligned so that the contact surfaces thereof are closedto each other when said first and second spring systems are deflectedsufficiently in opposite directions; said first and second springsystems differing from each other with respect to the values of at leastone of the parameters of loading mass and spring stiffness, so that thestatic deflections of said contact surfaces are substantially the samefor different values of gravitational and inertial forces acting on saidspring-loading masses.
 2. The motion sensor of claim 1, in which saidfirst and second spring systems are secured to said base at adjacentpositions and extend therefrom in the same direction in substantiallyparallel relationship to each other.
 3. The motion sensor of claim 2, inwhich each of said first and second spring mEans comprises acantilever-mounted leaf spring.
 4. The motion sensor of claim 1, inwhich said first and second spring means comprise first and secondcoaxial helical coil springs.
 5. A motion sensor, comprising: first coilspring means; means mounting said first coil spring means to permitsteady lateral deflection and lateral vibratory motion thereof; secondcoil spring means; means mounting said second coil spring means topermit lateral steady deflection and lateral vibratory motion thereof;said first and second coil spring means having respective first andsecond contact surfaces thereon positioned so that said contact surfacesare spaced from each other by substantially a fixed distance when saidsensor is oriented in different quiescent positions but contact eachother when said first and second coil spring means are set intovibration; said first and second coil spring means being helical andcoaxial, and said first coil spring means being positioned inside saidsecond coil spring means.